Extension ladder construction



April 4, 1939. T. EONVILLE EXTENSION LADDER CONSTRUCTION Filed July 9, 1936 e rm mu m l L@ m h H T L u||.v MN mwN EN n@ v o vN\ t o m Nu Il Patented Apr. 4, 1939 UNITE STATES PATENT FFHCE EXTENSION LADDER CONSTRUCTION Thomas Bonville, Portland, Maine Application July 9, 1936, Serial No. 89,793

5 Claims.

My present invention relates to improvements in the construction of extension ladders.

The difficulty of raising or extending these ladders is well known to all who use them. This diiculty is due to the weight of the slidable section and to friction. While efforts have been directed to minimize these causes, the inherent limitations on weight reduction appear to have resulted in the acceptance of all diiculties as unavoidable.

Several attempts have been made to reduce the friction and while an extended discussion of these proposed structures Would be burdensome, the general construction proposed and the objections thereto may be summarized. While these included anti-friction elements, the anti-friction elements were not properly formed or disposed in relation to the friction and to the stresses and strains to which such ladders are subjected in use.

I have solved the problem by providing antifriction U-shaped guides of a size to receive the side members of the ladder section. These guides not only minimize the friction, but also protect the wood from stresses and strains. These guides are adapted to replace conventional brackets and may be quickly attached either by the manufacturer or by the purchaser at low cost and without interfering with the construction or appearance of standard extension ladders.

In the drawing I have shown an embodiment of my invention which illustrates the advantages of my invention in solving the problems of extension ladder construction.

In the drawing:

Fig. 1 is a plan view of an extension ladder including my invention.

Fig. 2 is a side View of Fig. 1.

Fig. 3 is an enlarged sectional View along the lines 3-3 of Fig. 1.

Fig. 4 is a similar View along the lines 4-4 of Fig. 1.

Fig. 5 is a side View of the guide shown in Fig. 4, and

Fig. 6 is a front view of a modified form of guide for use in place of that shown in Fig. 3.

An extension ladder includes a bottom section A and an upper section B. Each section has side members I and rungs 2 which in the section B are shorter than those in the section A so that the section B will lie within the side members I of the section A and rest upon the rungs 2 of that section.

The sections A and B are slidably held together by brackets 3 and 4. In present constructions,

the brackets 3 are secured to the top surface of the side members vI of the section B near its lower end and are shaped to overlie the bottom of the side members I of the section A. Blocks 5 are generally added to the side members I of 5 the section B to make the sections A and B of equal width where the brackets 3 are to be added.

The brackets 4 are secured to the inner surfaces of the side members I of the section A near their upper ends and are formed to overlie the top ofthe side rails I of the section B. The brackets 4 serve as stops to limit the extension of the section B.

The construction thus far described, with the section B held by the brackets 3 and 4 against the rungs 2 of the section A, may be considered as conventional. As the means for raising and lowering the section B and the lock to hold the section B in desired position relative to the section A have no novel function in my invention, I have shown only a pulley 6 as suggestive of the former while the latter is shown generally at 1.

In accordance With my invention, the same construction is followed in order not to increase the width and depth of extension ladders and to permit my invention to be of utility by the manufacturer or the purchaser of standard ladders of the type under consideration. I form my brackets 3 and 4 to establish U-shaped recesses to slidably hold the side members I of the sections A and B respectively.

As shown in the drawing, the U-shaped recesses are established by forming or providing each of the brackets 3 with a ange 9 to enter between a block 5 and the top of a side member I of a section A and, in preferred embodiments, by forming or providing each of the brackets 4 with a flange I 0.

All surfaces of the U-shaped recesses are provided with rollers 8. The U-shaped recesses are of a size to provide slight clearance for the side members I and the rollers 8 are accordingly of small diameter. All surfaces of the U-shaped recesses are formed with slots II to accommodate the rollers 8 which are preferably mounted so that their axes of rotation are as closely related to the inner surfaces of the recesses as possible. Each roller 8 may be rotatably mounted on an axle 8a extending therethrough. The axles Ila may be secured to the inner surfaces of the U- shaped guides as at the ends of the slots I I in any desired way. This inexpensive and effective con,- struction is preferred as the long axle receives the wear ensuring long use. U-shaped recesses thus provided with rollers 8 make effective frictionless guides which as shown in Figs. 3 and 4 hold the section B away from the rungs 2 of the section A.

As the dimensions of the stock used (generally spruce or fir) are uniform and as my novel brackets 3 and 4 are capable of replacing standard brackets now in use, I use rollers of'. small diameter say one-quarter of an inch. When mounted as above described, the rollers 8 do not extend through the slots II more than is shown in the drawing and generally do not extend above the outer surfaces of the U-shaped recesses, and While being protected thereby the small rollers 8 do not cause the brackets 3 and 4 to stick out from the sides or above the sections A and B and do not increase the thickness or Width of an assembled extension ladder.

Within limits, modifications of my invention are permissible. As shown in Fig. 3, the flanges I0 may be omitted from the bracket 4 and a single larger' roller I2 maybe secured through each of the brackets 4 into the side members I of the section A'by a screw I3 which serves as its axle. "The bracket 3 may also be formed to provide a VU-shaped recess if the blocks 5 are omitted or removed, but I have preferred to illustrate my invention as applied to standard construction.

The use of a pair of rollers 8 on each surface of the U-shaped recesses is preferred as the bearing area is increased and the Wood protected from strains' or stresses encountered in use. For example, if a ladder is extended and supported by the side of a building, it yvvill be appreciated that the portion ofthe bracket 4 overlying the top of the side members I of the section B receives increased strain and the soft Wood is less likely to be marked by the construction used in accordance with my invention.V At the same time, it is noted that the size of these lrollers 8V present safety factors for if one bearing should be lost another bearing remains as even if all bearings Were removed, the Ueshaped recesses establish a close enough fit for the side members VI to permit the ladder to be usedV with;

safety.

` As all surfaces of the U-shaped recesses'are.

ard brackets and Will greatly'increase the ease` ci handling extension ladders andthe years o service that may beV had' from them.

What I thereforeclaim and desire to secure by Letters Patent is: i

l. A bracket for slidablyf. connecting the side members of extension ladder sections comprising" a portion adapted to be secured to a side member of one section and a U-shaped portion adapted to receive a side member of the other section, and a pair of rollers for each surface of said U-shaped portion, a slot for each of said rollers whereby said U-shaped recess may be made to provide a close t for said side member.

2. A bracket for slidably connecting the side members of extension ladder sections comprising a portion adapted tol be secured to a side member of one section and a U-shaped portion adapted to receive a side member of the other section, and a pair of rollers of a diameter in the order of one quarter of. an inch for each surface of said U-shaped portion, and a slot for each of said rollers whereby said U-shaped recess may be made to provide a close fit for said side member.

3. In combination with an extension ladder having section's,'a pair of brackets to slidably connect said sections, each of said brackets comprising a portion for attachment to a side member of one section and a U-shaped guide for the side member of said other section, the U-shaped guides of said pair of brackets being adapted to conne the side members of said last-named section with a clearance suci'ent to permit relative movement of Vsaid section, each portion of said U-shaped guide having a slot therethrough adjacent 'each edgejandnan anti-friction roller in each slot supported by said guide portion to prevent contact of said side members. With said guides. Y

4. In combination WithY an extension ladder liavingl sections, a pair of brackets to slidably" connect said sections, each of. said brackets corn-VV pr'ising a portion for attachment to `a side member'of one'sectionV and a U-shaped guide'fo the side member of saidother section, the U-shaped guides of said pair of brackets being adapted'to- Y confine the side members of said last-named section with a .clearance suilcient to permit relative movement-of said section, Veach portionA of?Y said'U-shaped guide'being'flat" and Vhaving aY slot therethrough adjacent each edge,Y and fan anti-'friction roller in each slot and mounted With`their-akes co-planarfvvith the outer` surface` t of said portion. l

5. Inwcornbination" withV an ,extensionv `ladder' havingsections, `a pair oi' brackets to slidably connect "saidsection's, each of ,said brackets com, prisingaportion for attachment to a side memy ber of one section and U-shape'dmg'uiding means for the side member of the other section, one portion"`of` said Yguiding lmeans comprising a bracket portion having avslot therethrough ad-l jacent each edge and having on assemblyof said bracketsron said sections a' clearance sufficient to permit relative movement of. saidsections and side members therewith. Y rIVI-IOMASY B ONl/'lLLE- Y '60' an anti-frictionrrollerin each slot supported by, Y said slotted portion to preventwcontact`ofjthe- Y 

